September 12: George Privon (UF Astronomy)
Title: Dynamical Models for Galaxy Mergers
Galaxy mergers in the local universe are known to trigger bursts of star
formation and the growth of supermassive black holes. The observational
evidence is broadly consistent with numerical predictions but detailed
comparisons are difficult due to ambiguities in the merger stages of
observed systems. I will describe detailed dynamical modeling of
observed mergers and the resulting constraints on the encounter geometry
and merger stage. I will then show how these models can be used to place
observed galaxy properties on a robust merger timeline, facilitating
more detailed comparisons with galaxy evolution simulations. Finally, I
will discuss prospects for these models as an avenue for constraining
galaxy merger rates and the timing of black hole growth in mergers.
September 19: Maria Charisi (Caltech)
Title: Quasars with periodic variability as sub-parsec supermassive black hole binary candidates
Supermassive Black Hole Binaries (SMBHBs) are expected to form frequently in galactic nuclei as a result of galaxy mergers. However, the observational evidence for such systems, especially for binaries at sub-parsec separations, remains sparse. Hydrodynamical simulations predict that SMBHBs produce quasar-like luminosities, with variability periodically modulated at the orbital period of the binary. I will present a systematic search for quasars with periodic variability in the Palomar Transient Factory and the detection of a population of candidate SMBHBs. Moreover, I will also discuss follow-up work to uncover additional evidence for the binary nature of the identified candidates, such as multi-wavelength signatures of relativistic Doppler boost.
September 26: Kyle Kremer (Northwestern Univ.)
Title: How Black Holes Shape Globular Clusters
Recent numerical simulations and observational indications have suggested that globular clusters (GCs) may contain large populations of stellar-mass black holes (BHs). This has important implications to gravitational wave astronomy, as GCs are understood to be efficient factories of merging BH-BH binaries. In this talk, I will examine ways BH populations influence the dynamical evolution and observable properties of GCs and also the discuss the dynamical formation of various types of BH binaries, including both low-mass X-ray binaries and gravitational wave sources that may be detectable by LIGO and LISA. Additionally, I will discuss the formation of accreting white dwarf binaries and their applications to LISA.
October 17: Marcos Santander (Univ. of Alabama)
Title: Unveiling the neutrino sky with IceCube
The IceCube Neutrino Observatory consists of a cubic kilometer of Antarctic ice instrumented with sensitive photodetectors deployed deep beneath the surface of the glacier at the geographic South Pole. In 2013 IceCube announced the detection of a cosmic flux of high-energy neutrinos in the TeV-PeV range. This breakthrough discovery has prompted a wide-ranging observational effort aimed at identifying the sources of the neutrino flux which combines IceCube measurements with observations spanning the entire electromagnetic spectrum. The detection of these sources would represent a major step forward for high-energy astrophysics that could reveal the acceleration sites of cosmic rays and provide a unique probe into the extreme environments in which these particles are produced. Recent multi-messenger campaigns have yielded the first evidence for a distant active galaxy as a high-energy neutrino source. This talk will introduce the IceCube detector, provide a summary of recent highlights from its wide research program concentrating on the search for neutrino sources, and outline how future instrumental developments may help pinpoint additional neutrino counterparts.
October 24: Raffaella Margutti (Northwestern Univ.)
Title: Astronomical Transients in the new era of multi-messenger Astrophysics
New and improved observational facilities are sampling the night sky with unprecedented temporal cadence and sensitivity across the electromagnetic spectrum. This exercise led to the discovery of new types of astronomical transients and revolutionized our understanding of phenomena that we thought we already know. In this talk I will review some very recent developments in the field that resulted from the ability to acquire a true panchromatic view of the most extreme stellar deaths in nature.
November 7: Wolfgang Tichy (Florida Atlantic Univ.)
Title: Gravitational waves from binary neutron star simulations
When compact objects such as neutron stars or black holes occur in binary configurations they can loose energy and spiral toward each other via the emission of gravitational waves. Waves from such inspirals have now been observed for both binary black holes and binary neutron stars. In order to analyze them it is important to have theoretical wave templates. We describe how numerical relativity simulations can be used to construct such templates. We start with a brief introduction to General Relativity and explain what black holes and neutron stars are. Then we explain how we conduct our numerical
simulations, and how they can be used to extract interesting information form observed gravitational wave signals. For example, it is possible constrain the equation of state of neutron star matter by comparing gravitational waves from actual detections and numerical simulations. To do so we have to conduct simulations for various star masses, spins and equations of state.
November 14: Jillian Bellovary (Queensborough Community College)
Title: Multimessenger Signatures of Massive Black Holes in Dwarf Galaxies
Recent discoveries of dwarf galaxies hosting active galactic nuclei (AGN) suggest that massive black holes (MBHs) may be a common occurrence in such low-mass systems. We examine the occupation and characteristics of MBHs in dwarf galaxies using the MARVEL-ous Dwarfs sample of high resolution cosmological simulations. We describe in detail the properties of seven dwarfs hosting MBHs, although none of them are AGN at any point during their histories. Approximately 50% of MBHs in the dwarfs are off-center, as a result of being perturbed by a merger with another dwarf galaxy. Our simulations include a subgrid model for dynamical friction; thus these off-center MBHs are a true dynamical consequence of mergers, and not a numerical effect. Since not every MBH in a dwarf is centrally located, some presupposed MBH-MBH mergers may not actually occur, which will affect the gravitational wave signal detected by LISA.
November 21: [Thanksgiving Week: No Seminar]
November 27, 2:00pm: Ann-Marie Madigan (CU Boulder)
[Note unusual date/time; joint w/ High Energy Seminar]
Title: The Importance of Being Eccentric
The dynamics of bodies on eccentric orbits largely determines the evolution of planetary systems and stars near massive black holes. In this talk I will review eccentric dynamics and demonstrate wide-ranging implications such as the orbital clustering of trans-Neptunian objects in the outer solar system (which motivates the planet nine hypothesis), ` double' galactic nuclei, and the tidal disruptions of stars by massive black holes in post-merger galaxies.
November 28: [No Seminar: Academic Jobs Panel]